Dual voltage regulating arrangement



Dec. 27, 1949 H. BANY 3 DUAL VOLTAGE REGULATING ARRANGEMENT Filed Sept. 2, 1948 v s Sheets-$1193 1- 8 :v I V In ventor: Herman Bany,

by His Attorney.

1949 H. BANY 2,492,729

DUAL VOLTKGE REGULATING ARRANGEMENT Filed Sept. 2, 1948 3 Sheets-Sheet 2 g 9 M I Inventor:

i' Herman Bany,

His Attorney.

Dec. 27, 1949 H. BANY 2,492,729

I I DUAL VOLTAGE REGULATING ARRANGEMENT Filed Sept. 2, 1948 3 Sheets-Sheet 3 Ihveht'orf: Herman Bany, I I by v His Attorney.

Patented Dec. 2-1, 19 9 DUAL VOLTAGE BEGUEATING ARRANGEMENT Herman Baiy, Lanldowne, Pa. assign:- to GeneralEleetric Company, a corporation New York Application September-2, 1043, Serial No. 47,388

1: Claims. (Cl. sacoey My invention relates to voltage regulating arrangements, and the principal obiect is to provide an improved dual voltage regulating arrangement suitable for use in an alternating current power system for regulating the voltages of both a particular load circuit and a power supply circuit therefor that also supplies other loads.

In accordance with my invention, the two circuits to be regulated are connected together through a variable voltage ratio power transfer device such as a regulating transformer, and one of the circuits, which can be designated as the incoming bus, is connected directly to the main power supply line and the other, which can be designated as the load bus, supplies a variable load and is also connected to a local source of volt amperes, such for example as a synchronous condenser.

In such a bus voltage ratio regulating arrangement, it is desirable that the voltages of both the load bus and the incoming bus be held at predetermined values during normal operation. Hence, another object of my invention is to automatically control the variable ratio voltage regulating transformer so as to maintain at a predetermined value the voltage of the incoming bus while at the same time automatically varying the output of the local source of volt amperes so as to maintain at a predetermined value the voltage of the load bus.

However, under abnormal load conditions when the synchronous condenser or other local source of volt amperes tends to become overloaded, its output necessarily must be limited to its fullrated value in order to prevent eventual overheating and resultant damage. Thus. under such abnormal conditions, it becomes impossible to maintain the voltages of both buses at their desired predetermined values. Hence, a selection must be made. Usually it is most important to hold the voltage of the load bus, at the desired predetermined value in order to obtain the proper operation of the load utihation apparatus even at some sacrifice in overall system or adjacent generating or substation operating conditions.

Thus, another object of my invention is to provide an automatic selective voltage regulating arrangement for regulating a selected one of the interconnected buses under excessive load conditions so as to cause the volt amperes, which are required for maintaining the load bus voltage at the desired value, to be supplied from the power system by automatically changing the volt- 2 age ratio of transformation of the regulating transformer, and consequently the incoming'bus voltage the necessary amount.

It is a further object of my invention, if for any reason the. synchronous condenser or other source of volt amperes connected to the load bus is not available or is shut down, to provide an automatic selective regulating arrangement such that the voltage of the load bus instead of that of the incoming bus is automatically regulated by the voltage regulating transformer at the expense of the incoming bus voltage, which then must operate unregulated.

Thus, the general object of my invention is under normal operating conditions to regulate the voltages of the load and the supply circuits separately, but under various abnormal conditions to give' the more important load circuit preference in the regulation of the corresponding voltages.

My invention will be better understood from the following description'of the accompanying drawings in which Fig. 1 diagrammatically illustrates one embodiment of the invention in an automatic regulating arrangement for a load circuit and .an alternating current supply circult therefor; Fig. 2 illustrates a modified form of automatic regulating apparatus that may be substituted for that shown below the line w-a in Fig. 1 if desired; and Figs. 3, 4 and 5 show further modifications similar to Fig. 2.

Referring to Fig. 1, i represents an A.-C. incoming bus connected to an A.-C. power system 6 through a suitable circuit breaker 5. A.-C.

. bus i supplies electrical energy to a load bus 4 through a suitable circuit breaker 3 and a suitable tap changing transformer 2. As shown, the transformer 2 is provided with a motor operated tap changer 31 for varying the number of active primary turns so as to change the voltage ratio of the transformer. The load bus 4 supplies load is through a suitable circuit breaker it. There is also normally in operation and connected to the load bus 4 through circuit breaker 1,.a local source ll of volt amperes, such as a synchronous condenser. The volt ampere source II is provided with a voltage regulator I! of any suitable type for automatically maintaining the terminal voltage of source ii and of load bus 4 at a predetermined value when source It is in operation.

Volt ampere source H is shown as a synchronous condenser provided with field winding 9. It may be started and placed into operation by any means well known in the art. For purposes of this invention, it will be necessary when the starting sequence has been completed for circuit breaker l to be closed connecting the armature of source I I to load bus 4 and for field breakor I4 to be closed connecting the field winding 8 to its source of excitation through contacts I8 of mm circuit breaker I4 and through the variable resistance element of regulator l1. Thus, when source II is in operation, contacts I3 of field circuit breaker I4 and contacts 8 of circuit breaker I are closed energizing the circuit of auxiliary relay 2I, thus causing contacts 23, 28 and 21 of this device to be opened and contacts 22, 24 and 28 to be closed..

The operating coil of voltage regulator I! is connected to the secondary winding of potential transformer 34 which has its primary winding connected to load bus 4 in accordance with practice well known in the art. Hence, regulator I1 by controlling the field current of source II through its variable resistance element maintains the voltage of load bus 4 at a predetermined value when source II is in operation.

In order to maintain the voltage of the incoming bus I at a predetermined value for different amounts of load I9 when source II is in operation and 'is not overloaded, I provide a voltage regulating relay 28 which has its operating coil connected to the secondary winding of potential transformer 35, which has its primary winding connected to incoming bus I, through contacts 22 of auxiliary relay 2 I, motor operated rheostat 33 and manually adjustable resistor 3|. Contacts 38 of relay 28 are closed when the voltage supplied to its coil circuit from incoming bus I is below a predetermined value, contacts 29 of relay 28 are closed when this voltage is above a predetermined value and neither the contacts 29 or 38 are closed when the voltage is at this predetermined value. The contacts 29, when closed, complete a circuit through contacts 26 of auxiliary relay 2| for reversible motor 20 of the tap changer 31 to decrease the voltage of the winding of transformer 2 connected to the bus I, and the contacts 30, when closed, complete a circuit through contacts 24 of auxiliary relay 2| for motor 28 of the tap changer 3'! to increase the voltage of the winding of transformer 2 connected to the incoming bus I. Hence, voltage regulating relay 28 maintains the voltage of incoming bus I through transformer 2 at a predetermined value by controlling the position of tap changer 31 by means of reversible motor 28. In order to limit the output of volt ampere source II to its full rated capacity when load I9 increases beyond a certain point, an overcurrent relay Ill is connected in any suitable manner in the output circuit of source I I and is provided with contacts I2 and I3. Contacts I2 of relay II are closed when .the output of source II is above its full rated capacity, contacts I3 of relay II are closed when the output of source II is below its full rated capacity and neither the contacts I2 or I3 are closed when the source II is delivering approximately its full rated capacity.

In order for relay I 8 to prevent the overloading of source II, its contacts control the position of motor operated rheostat 33 which is connected in series with the coil of voltage regulatingrelay 28 when source II is in operation. When source II is operating below full rated capacity, contacts I3 of relay I close and operate reversible motor 33 of the rheostat mechanism 38 in the direction to increase the resistance of rheostat 33 and thus normally when source II is operating below full rated capacity rheostat 33 is in the maximum resistance position as shown in Fig. 1. When the output ofsource I I increases above its full rated capacity, contacts I2 of relay l8 close and operate reversible motor 38 of rheostat mechanism 88 in the direction to decrease the resistance of rheostat 33. This has the ell'ect of decreasing the voltage setting of regulating relay 28 which thereupon closes its contacts 29. These contacts, as previously described, complete a circuit for reversible motor 20 of the tap changer 31 to decrease the voltage of the winding of transformer 2 connected to the incoming bus I and thereby increase the voltage of the transformer winding connected to load bus 4. By thus increasing the voltage of load bus 4 with respect to incoming bus I, additional reactive volt amperes are supplied from incoming bus I through transformer 2 to load bus 4 and to the predominantly reactive load I9. This relieves source II of some of the reactive volt ampere output it has been supplying to load I9 and so when its output has been reduced so that it again delivers approximately full rated output .to load bus 4, the contacts I2 of relay I0 re-open. This interrupts the circuit to motor 36 and rheostat 33 remains in position to provide the proper setting of voltage regulating relay 28 to give the correct value of voltage on incoming bus I which will prevent overloading of source II, but will still allow it to deliver full rated output to load bus 4. When load I9 decreases slightly so that ,the output of source II again decreases below full rated value, the contacts I3 of relay III, by controlling motor 36, will re-position rheostat 33 to another value to give the proper setting of relay 28 so that source II will continue to operate at approximately full rated load. If a further load reduction occurs, the contacts I3 of relay I0 will again close, and if this reduction is sufficient, they will remain closed, causing rheostat 33 to run to the maximum resistance position thus permitting relay 28 through tap changer 3'! and transformer 2 to maintain a predetermined value of voltage on incoming bus I.

Varying the ratio of the transformer so as to increase the load bus voltage from the system decreases the field excitation of the synchronous condenser because it will hold the load bus voltage constant, and it therefore supplies less reactive (overexcited) vars to the load, and the system must make up the deficiency.

Likewise, varying the ratio of the transformer so as to decrease the load bus voltage from the system increases the field excitation of the synchronous condenser because it will hold the load bus voltage constant, and it therefore supplies less capacitive (underexcited) vars to the load, and the system must make up the deficiency.

If for any reason the source II of volt amperes is not available or is shut down. as may be the case when load I9 is sufliciently low, so that circuit breaker I and field circuit breaker I4 are open, then the coil circuit of auxiliary relay 2| is opened by the contacts I5 of field circuit breaker I4 and by contacts 8 of circuit breaker I. This opens the contacts 22, 24 and 23 of auxiliary relay 2I and closes the contacts 23, 25 and 21. The coil circuit of voltage regulating relay 28 is thus transferred from the secondary winding of potential transformer 35, which has its primary winding connected to incoming bus I, to the secondary winding of the potential transformer 34, which has its primary winding connected to load bus 4, by means of contacts 22 and 23, respectively, of auxiliary relay 2i. when this transfer has been made. motor operated rheostat 33 and manually operated adjusting resistance 3|, associated with the secondary winding of potential transformer 33, are also removed from the coil circuit of relay 23 and manually operated adjusting resistor 32, associated with the secondary winding of potential transformer 33, is inserted in their place. Manually operated adjusting resistors 3| and 32 are provided for the purpose of making different settings for voltage regulating relay 28 depending upon whether it is regulating the voltage of incoming bus i or load bus 4.

Regulating relay 28 is now responsive to the voltage of load bus 4 instead of to the voltage of incoming bus I. The circuits from the contacts 23 and 33 of relay 28 to motor 23 of tap changer 31 have now been reversed by the change in position of auxiliary relay 2| so that now on overvoltage on load'bus l the contacts 23 of relay 28 operate the reversible motor 23 of tap changer 31 through the contacts 21 of auxiliary relay 2| in such a direction as to lower the voltage of the winding of transformer 2 connected to load bus 4. n undervoltage on load bus 4, contacts 30 of relay 28 operate the motor of tap changer 31 through the contacts 23 of auxiliary relay 2| in the direction to raise the voltage of the winding of transformer 2 connected to load bus 4. Hence, regulating relay 28 now maintains the voltage of load bus 3 at a predetermined value through tap changer 31 of transformer 2 when source Ii is not in operation.

The arrangement described above includes provisions for readiusting the setting of voltage regulating relay 28 only when source II is overloaded due to supplying reactive volt amperes to the load or system in excess of its rating. No provision is shown for readiusting the setting of relay 28 if source II should have reached the limit of its capacity in supplying capacitive volt amperes. If volt ampere source II is of the type and is so applied in service that it can be overloaded by delivering capacitive volt amperes in excess of full rated capacity, then relay means will have to be provided to detect this condition. These must prevent the operation of motor operated rheostat 33 to decrease its resistance under these conditions since its operation in this manner would merely tend to make the source Ii deliver additional capacitive volt amperes instead of relieving it of some and this incorrect action will further be cumulative, resulting in unstable operation.

Hence, for loads that are predominantly capacitive and if the power source H is such that it can be overloaded under these conditions, the construction and control of the motor operated rheostat 33 will have to be so modified that the setting of voltage relay 28 is raised at this time when source H is overloaded. The necessary modifications to accomplish this as well as to obtain proper operation for predominantly reactive loads, as already described, are shown in Fig. 2.

In order to detect whether source I i is supplying reactive or capacitive volt amperes to the load or system, I provide var relay '41 which is connected to the circuit of source ii in any suitable manner so that contacts 4! are closed while the source Ii is over-excited and supplying reactive volt amperes, and the contacts 43 of relay 41 are closed while the source I I is underexcited and is supplying capacitive volt amperes."

The functions of var relay 41 for the purpose of this invention can also be performed by a relay, in the field circuit 3 oi. the condenser II,

which is responsive to the amount of condenserfield current. At field currents above a predetermined value, the condenser will be delivering reactive volt amperes; at field currents of a predetermined value, the power factor of the condenser II will be substantially unity; and at field currents below a predetermined value, condenser II will be delivering capacitive volt amperes. Such a field current responsive relay can have its contacts connected to function in exactly the same manner as the contacts of the var relay 1 in Figs. 2, 3 and 4 and fulfill exactly the same functions.

In order to be able to raise the setting of voltage regulating relay 28 when source II is supplying capacitive volt amperes in excess of its rating and also to be able to lower its setting when supplying predominately reactive volt amperes in excess of its rating, as has been described previously in connection with Fig. 1, I modify motor operated rheostat 33 by providing additional resistance steps and arranging the construction and control of this rheostat so that normally it is positioned in the approximate mid-point of its travel, instead of in the maximum resistance position as was previously described in connection with Fig. 1.

Two mid-position switches ll and 42 are provided and so arranged that switch 42 is closed only when the arm of rheostat 33 is in the decreased resistance position and switch H is closed only when the arm of rheostat 33 is in the increased resistance position. Switches 33 and 40 are conventional limit switches open only at the all-out and all-in positions, respectively, of'rheostat 33.

In order to maintain the voltage of the incoming bus I at a predetermined value for different amounts of load l9 when source I i is in operation and is not overloaded, the operation of the equipment is just the same as has been previously described for Fig. 1. Rheostat 33 is, however, in its approximate mid-position with switches 45 and 32 both open and the amount of resistance normally in the coil circuit of voltage regulating relay 28 is the same as that present in the all-in position of the rheostat in Fig. 1.

However, when source H becomes overloaded and overcurrent relay l8 closes its contacts I2, the position of the contacts of var relay 41 determines whether rheostat 33 will move in the direction to decrease or increase resistance in series with the coil of voltage regulating relay 28. If the output of source II is predominately reactive as was previously assumed and described in connection with Fig. 1, motor 38 of rheostat 33 is moved in the direction to decrease the resistance through the contacts l2 of relay Iii, contacts 45 of relay ti and limit switch 39 of rheostat 33'. Voltage regulating relay 28 thus has its setting lowered and it controls the motor 20 of tap changer 37 to decrease the voltage of incoming bus I as before. When the output of source It decreases to the point where contacts l3 of relay in reclose, the rheostat 33 is moved towards its mid-position by motor 36 through contacts i3 of relay It, the contacts of position switch 42 and limit switch '40 of rheostat 33. Contacts 38 of relay 28 control the motor 28 of tap changer 31 to increase the voltage of incoming bus i as before.

If the output of source ii is predominately capacitive and exceeds the setting of relay Ill, motor 36 of rheostat 33 is then moved in the direction to increase its resistance through the contacts I2 of relay I0, contact 43 of relay 41. and the limit switch 40 of rheostat 33. Voltage regulating relay 23 thus has its setting raised and through contacts 30 it controls motor 20 of tap changer 31 to increase the voltage of the winding of transformer 2 connected to incoming bus I and to decrease the voltage of the winding of transformer 2 connected to load bus 4. By thus attempting to decrease the voltage of load bus 4 with respect to incoming bus I, additional capacitive volt amperes are supplied from the incoming bus I through transformer 2 to load bus 4 and to load I5, thus relieving source II of some of the capacitive volt ampere output it has been supply-v ing to load I3. When the output of source II decreases to a point where the contacts I3 of relay III reclose, then rheostat 33 is moved toward its mid-position by motor 35 through the contacts I3 of relay III, contacts of position switch H, and limit switch 39 of rheostat 33. Contacts 23 of relay 23 control the motor 20 of tap changer 31 to again decrease the voltage of incoming bus I so that eventually relay 28 will again maintain a predetermined value of voltage on incoming bus I.

Rheostat 33 is positioned in the approximate mid-position through the contacts I3 of relay I when these remain closed and through the respective contacts of position switches 42 or H, either when source II is in operation or is shut down.

This regulating scheme shown in Fig. 2 will thus maintain the voltage of load bus 4 at a predetermined value when source II is in operation and will hold the output of source II within its full rated capacity irrespective of whether its output is predominately reactive or capacitive. When source II is shut down, voltage regulating relay is transferred, as was done in Fig. l, to-hold the voltage of load bus 4, instead of incoming bus I, in exactly the same manner as previously described for Fig. 1.

If source II is a synchronous condenser, as is here shown, commercial designs of these machines are usually such that they are unable to put out a suiilcient amount of capacitive volt amperes to overload them. Hence, overload relay III, ii the output of source II is in capacitive volt amperes, will usually not be able to open its contacts l3 or close its contacts I2. Hence, it will be necessary toprovide a lower calibration for relay III when the condenser is delivering its limit of output in capacitive volt amperes or to provide some other means of detecting this condition.

Fig. 3 shows how the recalibration of overload relay III can be accomplished. Relay I0 is provided with recalibrating coil 43 which when energized through contacts 43 of relay 4'', closed when source I l is underexcited and is supplying capacitive volt amperes, reduces the overcurrent setting of relay III the desired amount. Adjustable resistance 53 provides the required adjustment for the purpose. of relay 4'! cooperate to control the position of motor operated rheostat 33 as previously described for Fig. 2-the diiference is merely that relay III operates in response to a lower value of capacitive volt ampere output of source I I.

It is also possible instead of providing a recalibrating means for relay It to provide an additional relay 55 as shown in Fig. 4 similar to relay III but with a lower calibration to control the position of rheostat 33 when the condenser is operating underexcited and delivering capacitive volt amperes to the system. Contacts 51 of relay 53 through contacts 43 of relay 4'! cause motor 35 The contacts of relay I 0 and to rheostat 33 to increase its resistance on an excess output of capacitive amperes or source II due to underexcitation, and contacts I2 oi. relay 58 through contacts 45 of relay 4'! cause motor 36 of rheosta *3 to decrease its resistance on excess output of reactive volt amperes due to overexcitation. Motor 36 of rheostat 33 runs rheostat 33 to the mid-position -as determined by position switch H or 42 it source II is supplying capacitive volt amperes not in excess of the setting of relay 56, through contacts 58 of relay 5'! and contacts I3 of relay ID, in series. If source I I is supplying reactive volt amperes below the setting of relay I 0, then motor 33 of rheostat 33 runs rheostat 33 to the mid-position as determined by position switch 4! or 42. through contacts I3 of relay I0 and contacts 53 of relay 41, which are closed when source II is operating overexcited and supplying reactive volt amperes, in series.

Another method of detecting that source H has reached its maximum output on underexcitation is to provide an undercurrent relay 53 with coil 55 in the field circuit 9 of source I I as shown in Fig. 5. The use of such a relay, whose contacts 52 will close at practically zero field current and whose contacts 5| will close at a slightly higher value of field current will take the place of the reactive relay 41 in Figs. 2, 3 and 4 and the reduced setting of relay Ill obtained by the use of the recalibrating coil 49 on relay III in Fig. 3 and relay 56 in Fig. 4. Polarizing coil 54 is provided on relay 53 in a manner well known in the art so that contacts 5I and 52 can be made to operate at low current values through coil 55.

When contacts 52 of relay 53 close indicating that source I I is supplying the desired maximum capacitive volt amperes to the loader system, motor 36 of rheostat 33 is operated to increase the resistance of rheostat 33. When contacts I2 of overcurrent relay I0 close, motor 36 of rheostat 33 is operated to decrease the resistance of rheostat 33. When contacts 5| of relay 53 and contacts I3 of relay I0 are closed, the motor 33 of rheostat 33 will run rheostat 33 to the midposition through the contacts of rheostat position switch M or 42, whichever is closed. The results of the aforesaid operations of rheostat 33 on the calibrating of relay 28 on the voltage held on the incoming bus I have been previously described in connection with the scheme 01. operation for Fig. 2.

It is possible in the schemes shown in Figs. 2, 3, 4 and 5 to provide two identical rheostats of the type shown in Fig. 1 instead of a single rheostat with double the resistance and midposition switches 4| and 42. The control circuits of a scheme with these two rheostats would be arranged so that one of the rheostats, normally in the position with the resistance all in, would be controlled to decrease its resistance when the condenser I I has reached its rated output in reactive volt amperes as already described for Fig. 1; and the other rheostat, normally in the resistance all-out position, would increase its resistance when the condenser has reached its maximum output of capacitive volt amperes. The use of the single rheostat 33 with mid-position switches is merely a more economical and practical arrangement.

It is even possible to omit rheostat 33 entirely in all of these schemes by placing the contacts of relays III in Fig. l, of relays I0 and 41 in Figs. 2 and 3, and of relays 56, I3 and 41 in Fig. 4 and of relays III and 53 in Fig. 5 directly in the control eircuiis: of motor I. of tap changer I! in cooperntion with the contacts 29 and II of volt regulatin relay 28 in a manner well known in the art. The use of rheostat 13, however, has the advantage that it provides greater segregation and simplicity of control which is desirable for this type of installation.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A voltage regulating arrangement comprising a variable ratio power transformer for. interconnecting an alternating current power supply circuit with a load circuit, a separate source of volt amperes for supplying the load circuit. an electroresponsive device responsive to the output of said source, and means controlled by said device for varying the ratio of said transformer to control the voltage of the supply circuit.

2. A voltage regulating arrangement comprising a variable ratio power transformer for interconnecting an alternating current power supply circuit with a load circuit, a separate source of volt amperes for supplying the load circuit, an electroresponsive device responsive to the output of said source, means controlled by said device for varying the ratio of said transformer to control the voltage of the supply circuit, and means effective when said source is inactive for varying the ratio of said transformer to control the voltage of the load circuit.

3. A dual voltage regulating arrangement comprising a variable ratio power transformer for interconnecting an alternating current power supply circuit with a load circuit, means including a variably excited condenser for separately regulating the voltage of the load circuit, an electroresponsive device responsive to the var output of said condenser, and means controlled by said device for selectively varying the ratio of said transformer and the excitation of said condenser to control the voltages of said circuits under varying load conditions.

4. A voltage regulating arrangement comprising a variable ratio power transformer for interconnecting an alternating current power supply circuit with a load circuit, means including a variably excited condenser for separately reguiating the voltage of the load circuit, an electroresponsive device responsive to the excitation of said condenser, and means controlled by said device for varying the ratio of said transformer to control the voltage of the supply circuit.

5. A dual voltage regulating arrangement for use in an alternating current system comprising means including a variable voltage ratio alternating current power transfer device for supplying a variable load from the system, voltage regulating means including a variable output source of volt amperes connected to the load circuit of the device to maintain the load voltage substantially constant, and an electroresponsive regulating device responsive to the voltage of the supply circuit of the device and having means controlled thereby for varying the voltage ratio of the transfer device to control the voltage of the supply circuit.

6. A voltage regulating arrangement for an alternating current power supply line comprising a variable voltage ratio alternating current power transformer for supplying a variable load from the line, voltage responsive means connected to be responsive to the load voltage of said transformer and having a synchronous condenser connected to be controlled thereby for maintaining said load voltage substantially constant, and a i0 voltage responsive device connected to be responsive to the line voltage of said transformer and having means controlled thereby for vary ing the voltage ratio of said transformer to control the line voltage.

7. A voltage regulating arrangement for use in an alternating current power system having an incoming power bus and a load bus comprising means including a tap transformer for interconnecting said buses, a synchronous condenser for connection to the load bus and having automatic excitation regulating means for maintaining the load bus voltage substantially constant, and regulating means including a relay for responding to variation of the voltage of the incoming power but from a predetermined value and tap changing mechanism operable under the control of said relay for varying the voltage ratio of said transformer to return said incoming bus voltage substantially to said value.

8. A voltage regulating arrangement for an alternating current power supply line comprising a variable voltage ratio alternating current power transfer device for supplying a variable load from the line, a voltage responsive device connected to be responsive to the load voltage of the device and having a variable output source of volt am peres controlled thereby for maintaining the load voltage substantially constant, an adjustable voltage responsive device connected to be responsive to the line voltage of the transfer device and having means controlled thereby for varying the voltage ratio of said device to control the line voltage and electroresnonsive means responsive to variations in the output of said source for adjusting said voltage responsive device.

9. A volta e ratio regulating arran ement for use in an alternatin current power system comprising means including a variable voltage ratio transformer for supplyin a variable load from the system. volta e regulating means including a variable output synchronous condenser connected to the load circuit of said transformer to maintain the load voltage substantially constant, an adjustable volta e regulating device responsive to opposite variations of the voltage of the supply circuit of said transformer and having means controlled thereby for correspondingly varying the voltage ratio of said transformer, and electroresponsive means responsive to opposite variations of the output of said condenser for correspondingly adjusting said voltage regulating device.

10. A voltage regulating arrangement for an alternating current supply line comprising a variable voltage ratio alternating current power transfer device for supplying a variable load from the line, voltage regulating means including a variable output source of volt amperes normally connected to the load circuit of the device to maintain the load voltage substantially constant, and a voltage responsive device normally connected to be responsive to variation of the line voltage of the transfer device and having operating means controlled thereby for varying the voltage ratio of the transfer device to regulate the line voltage thereof, and means including an automatic transfer relay for connecting said voltage responsive device to be responsive to the voltage of the load circuit of said transfer device and reversing the control of said operating means to regulate the load circuit voltage when said source is disconnected.

11. A voltage regulating arrangement for use in an alternating current power system having guano an incoming power bus and a load busccmprising a variable voltage ratio transformer for interconnecting the buses, voltage responsive revere; ible control means for varying the voltage ratio of the transformer. a variable output synchronous condenser normally connected to the load bus and having excitation regulating means for maintaining the load bus voltage substantially constant, and means including an automatic transfer relay for connecting the voltage responsive control means to be responsive to variation of the incoming bus voltage when said synchronous condenser is connected to the load bus and to be reversely responsive to variation of the load bus voltage when the synchronous condenser is disconnected.

12. A voltage regulating arrangement for use in an alternating current power system comprising means including a voltage ratio regulating transformer for supplying a variable load from the system, voltage regulating means including a variable output synchronous condenser adapted to be connected to the load circuit of said transformer to maintain the load voltage substantially constant, ratio control means for said transformer including a voltage responsive device normally responsive to variation of the supply voltage of the supply circuit of said transformer from a predetermined value, and electroresponsive means responsive to the var output of said synchronous condenser for varying the response of said device.

HERMAN BANY.

N e references cited. 

